2D dual drainage models

[Ravn]

I'd like to ask your opinion about 2 dimensional (2D) dual drainage models.

What benefits you think one is getting by modelling the drainage network with 2D flow model instead of simplifying areas to sub-catchments as well as simplifying their hydraulic and hydrologic phenomena?

Is there any major disadvantage - if price is not taken into account?

Best regards,

Johann.

 

[blueoak]

I may be off base on the question, but ... I see 2D's such as RMA2 and FLO-2D for water surface models. These are typically for flood risk, because they give better velocity numbers in the edge areas or stagnant spots. As for hydrology like CASC2D I think when the GIS gets better they will be good just because they will be so automatic. THe big disadvantage is regulators have trouble learning a whole new (costly) system for review and most people tend to calibrae them off 1D models.

 

[cvg]

2d (hydraulic) models may be better for modeling things such as alluvial fan / plains, sheet flows, flow through dams, over dams and along levees, especially when the water level is controlled by ponding and mass balance, rather than by the typial 1 dimensional channel or pipe flow.

 

[Ravn]

I tried to ask about the benefits of the more accurate surface flow achieved with a 2D surface flow model in urban environment.

In the "basic" urban drainage models, the surface flow is very simplified: One does have a catchment that is described with different parameters like pervious/impervious ratio, total area, average slope, roughness, infiltration, average length and width etc.

Is this kind of approach accurate enough in urban environment?

One catchment area (for an inlet, for example) can have "channels" in many elevations (pavements, roadway) and individual sources of significant discharge in a form of large roofs that discharge all water into the inpervious surface.

I'm also interested in modelling permeable materials. Could 2D surface flow models bring something more into this than simplified 1D models, when the aim is to study possible ways to decrease urban floods?

How about making flood maps in urban regions due to inlet surcharges, for example?

How could these problems be solved with/without 2D surface model combined to stormwater drainage network (1D software like SWMM and MOUSE).

I'd appreciate any comments.

Johann.